1. Field of the Invention
The present invention relates to a sheet treating apparatus, and more particularly it relates to a sheet treating apparatus for successively receiving sheets such as copying paper discharged from an image forming apparatus such as a copying machine, a printing device or a laser beam printer after image formations and for effecting treatment such as alignment and stitching of the sheets and for discharging and stacking the treated sheets onto a stacking portion.
2. Related Background Art
In conventional image forming apparatuses such as printing devices, copying machines, printers or the like, sheets on which images are formed in a main body of the image forming apparatus are temporarily stacked on a treating tray (first stacking means) by a pair of discharge rollers (sheet discharging means) within a sheet treating apparatus, where, sheet treatment such as alignment and stitching of a sheet bundle is effected. Thereafter, the treated sheet bundle is bundle-discharged onto a stack tray (second stacking means) outside the main body by bundle discharging means.
A trailing end of the sheet bundle discharged on the stack tray is detected by a sheet surface height detecting sensor, and, on the basis of detection, an uppermost level of the sheets on the second stacking means is maintained to a predetermined level.
However, in such a conventional apparatus, if the sheet bundle discharged on the second stacking means is curled, erroneous detection of the sheet height is effected by the sheet height detecting sensor, so that the proper sheet height cannot be detected.